1. Field of the Invention
The present invention is generally directed to correction of refractive error and/or aberrations of the eye. Although specific reference is made to corneal onlays placed on an eye, embodiments of the present invention can be used in many applications where a lens is fabricated and/or adhered to tissue.
The eye includes several tissues that allow patients to see. The eye generally includes a cornea, a lens and a retina. The cornea and lens focus light on the retina so as to form an image that can be perceived by the patient. The cornea of the eye is an anterior tissue of the eye that is clear in healthy eyes. The lens is disposed posterior to the cornea and can also focus light to allow a patient to see. The aqueous humor is a fluid disposed between the cornea and lens. The retina is disposed posterior to the lens and includes many photo receptors to sense an image formed on the retina by the cornea and lens.
Many patients suffer from some form of optical defect of the eye. Commonly known optical defects of the eye include refractive errors such as nearsightedness, also referred to as myopia, far sightedness, also referred to as hyperopia, and astigmatism. In addition, many eyes have some level of higher order aberration such as coma, and spherical aberration. These higher order aberrations can be measured with optical systems such as wavefront systems, and may affect vision in some patients, for example with large pupil sizes at night.
Work in relation to embodiments of the present invention suggests that current techniques to correct optical defects of the eye may be less than ideal in at least some instances. Eyeglasses and contact lenses may not be suitable for some patients, and in many instances may not correct higher order aberrations of the eye. For example, eyeglasses can be difficult for active patients to wear. In at least some instances, contact lenses may cause irritation of the eye. Many of the current surgical methodologies involve cutting and/or removal of tissue. In at least some instances, this cutting and removal of tissue may weaken the eye and limit the size of optical correction on the eye. In at least some patients, the size of optical correction may be smaller than the pupil at night, such that aberrations may be induced by the surgery that is intended to correct vision of the eye. Examples of surgeries that cut and/or remove tissue include photorefractive keratectomy (hereinafter “PRK”) and laser assisted in situ keratomileusis (hereinafter “LASIK”).
One approach that provides an optical correction by adding material to the eye is to place a lens on or in the cornea of the eye, referred to as corneal onlays and corneal inlays, respectively. Corneal onlay generally refers to a lens placed on the eye under an epithelial layer and/or on an exposed surface after the epithelial layer has been removed. In human patients with normal eyes the exposed tissue layer under the epithelium is referred to as Bowman's membrane. With corneal onlays in human patients with normal eyes, the corrective lens can be placed on Bowman's membrane after removal of the corneal epithelium. In human patients who have undergone PRK and some animals, the layer of tissue exposed with removal of the epithelium can include corneal stroma, and an onlay positioned on such patients can be positioned on corneal stroma.
Although corneal onlays may provide some advantages over current methodologies that remove tissue, work in relation to embodiments of the present invention suggests that current corneal onlays may be less than ideal. One problem that may occur with corneal onlays in some instances is that epithelial tissue may grow under the onlay so as to dislodge the onlay from the eye. Many patients would like to receive correction of wavefront aberrations of the eye. Wavefront correction that may require that the onlay lens have a complex shape on the eye that is within a few microns, or less, of the intended shape. At least some of the current methodologies of fabricating and placing corneal onlays on the eye may not be able to consistently provide complex shapes on the eye with the required accuracy for all patients. Because of the above potential short comings of corneal onlays and current refractive surgeries, at least some patients may receive a correction that is less than ideal.
In light of the above, it would be desirable to provide improved treatments for epithelial defects of the cornea. Ideally, these treatments would avoid at least some of the deficiencies of known techniques while providing improved patient vision.
2. Description of the Background Art
The following patents and publications may be relevant to the present application U.S. Pat. Nos. 4,126,904; 4,268,131; 4,346,482; 4,452,776; 4,452,925; 4,563,779; 4,581,030; 4,612,912; 4,624,669; 4,676,790; 4,693,715; 4,715,858; 4,799,931; 4,810,082; 4,834,748; 4,851,003; 4,923,467; 4,973,493; 4,979,959; 4,983,181; 4,994,081; 5,019,097; 5,108,428; 5,112,350; 5,114,627; 5,156,622; 5,163,596; 5,171,318; 5,192,316; 5,196,027; 5,213,720; 5,244,799; 5,263,992; 5,292,514; 5,401,508; 5,489,300; 5,522,888; 5,552,452; 5,713,957; 5,716,633; 5,836,313; 6,055,990; 6,090,995; 6,454,800; 6,544,286; 6,607,522; 6,645,715; 6,689,165; 6,702,807; 6,880,558; 7,004,953; 7,077,839; 7,229,685; US2004/0170666; US2005/028723; US2006/0034807; US2006/013050; US2006/0134170; US2006/0246113; and US2007/002046.